Prior art inductive elements are shown in FIG. 24 (a) to FIG. 24 (c).
In the drawings, a plate material such as iron alloy was blanked to form a zigzag part 1 in the middle, and straight terminal parts 2 were provided at both ends of the zigzag part 1.
Prior LC filters are shown in FIG. 25 (a) to FIG. 25 (d).
In FIG. 25 (a), a U-shaped lead wire 4 was inserted into a pair of tubular sintered ferrite cores 3, and a capacitive element 5 with a lead was connected to the middle of the lead wire 4. In FIG. 25 (b), using a formed bobbin 8 having brims 6, 7 at both ends and in the middle, leads for external connection 9 were inserted into the brims 6 at both ends of the formed bobbin 8, a capacitive element 11 with leads was inserted into a indented part 10 of the middle brim 7, windings 12 were wound between the brims 6 and 7 of the formed bobbin 8, outgoing wires of the windings 12 were wound around the leads for external connections 9 and the lead of the capacitive element 11 was connected by soldering to the windings 12.
The prior art LC filter shown in FIG. 25 (c) includes a pair of drum cores 14 having a coil 13, and a capacitive element 15 having a pair of axial leads. An axial lead is connected to the coil.
In FIG. 25 (d), after forming four penetration holes 16 in a U-shaped ferrite core 17, lead wires were inserted into the penetration holes 16, and the penetration holes 16 were interconnected with conductors 18 to form an inductive element, while a capacitive element 19 was disposed in a indented part of the U-shaped ferrite core 17 to connect with the conductors 18, thereby forming an LC filter. The prior LC filters were generally molded with resin or encased with resin box.
The prior inductive components, LC filters and other electronic components were manufactured as shown in FIG. 26 (a) to FIG. 26 (d).
In accordance with the drawings, an electric conductive hoop 21 was blanked in an electronic component element 20 to form a terminal plate 22, which was bent, connected and set in molding dies 23. Resin was then poured into the molding dies 23 so as to be formed into the state as shown in FIG. 26 (b). The electric conductive hoop 21 and terminal plate 22 were next cut off and separated to manufacture an intermediate part as shown in FIG. 26 (c). The terminal plate 22 was then bent along the flank of an exterior mold 24, thereby fabricating an electronic component for surface mounting as shown in FIG. 25 (d). That is, the electronic component manufactured by this method possessed a pair of terminals 22 having bottom terminals 22a and side terminals 22b on the flanks of the exterior mold 24. When forming the exterior mold, the resin deposited on the surface of the bottom terminal 22a and burrs were formed. As a result, serious interference with soldering occurred when mounting on the surface of the electric circuit. Thus a deburring process was needed. As a result, the productivity was low. In addition, the terminal plate 22 was first separated from the electric conductive hoop 21 and then bent along the side surface from the corner of the exterior mold 24. In this case, the bent part was not square due to spring-back of the terminal plate 22. Furthermore, either the side terminal 22b was cleared from the flank of the exterior mold 24 or the bottom terminal 22a was lifted from the bottom of the external mold 24. Therefore, surface mounting quality was impaired, and the soldering performance with regard to mounting was poor.
Accordingly, as shown in FIG. 27, it was proposed to compose molding dies 25 to as to draw out the terminal plate 22 vertically from the bottom of the exterior mold 24. However, this method requires high precision processing of the drawing part of the terminal plate 22 of the molding dies 25. Furthermore, the terminal plate 22 of the electric conductive hoop 21 is typically preliminarily bent in square direction, and the terminal plate 22 could not be bent completely at a right angle. Moreover, as shown in FIG. 28 (a) to FIG. 28 (d), the terminal plate 22 integrated with an electric conductive hoop 21 was drawn out from the side of the exterior mold 24, the terminal plate 22 was cut off to a specified dimension from the electric conductive hoop 21 as shown in FIG. 28 (b), and separated, and then this terminal plate 22 was bent squarely as shown in FIG. 28 (c). The terminal plate 22 was further bent along the flank of the exterior mold 24, thereby forming the bottom terminal 22a and side terminal 22b.
Although the inductive element shown in FIG. 24 (a) to FIG. 24 (c) is effective as an independent inductive component when molded with resin involving magnetic powder, two inductive components are typically coupled. When further combined with a capacitive element, a large sized device was realized which required labor for assembly. Furthermore, productivity was low.
Nevertheless, by using a resin which includes magnetic powder, the magnetic coupling increases, the attenuation is enlarged, and an eddy current is generated in the capacitive element to increase the loss (tan .delta.), thereby increasing the trap attenuation. Furthermore, when the zigzag part 1 was molded with resin in a hollow state, the zigzag part was deformed by the resin injection pressure which resulted in the generation of of layer shorts and/or the lowering or variance of inductance. Furthermore, the stable production could not be realized.
In the LC filters shown in FIG. 25 (a) to FIG. 25 (d), labor was typically required to insert lead into the ferrite core, and plating of high reliability was typically needed. Moreover, there were many places where the outgoing wire of the winding and the leads are connected, the productivity was low, and disconnections and faulty connections were likely to occur in the connections between the outgoing wires and leads.
In the prior method of manufacturing electronic components, the inductive element was cut off and separated from the electric conductive hoop, and bent as shown in FIG. 28 (c). However, the terminal could not be set tightly along the flank of the exterior mold.